Tripot type constant velocity universal joint

ABSTRACT

A tripot type constant velocity universal joint comprises a first rotary member provided with three sets of track surfaces each consisting of two parallel planar surfaces, a second rotary member provided with three trunnions corresponding to the track surfaces, and cylindrical roller assemblies loosely fitted to the trunnions and fitted on the track surfaces. The cylindrical roller assemblies are pivoted around corresponding points on the axes of the trunnions. The roller assemblies have a pivot controlling member for controlling pivot of the roller assemblies.

This is a division of patent application Ser. No. 069,759, filed July 6,1987 (now U.S. Pat. No. 4,854,917 issued Aug. 8, 1989).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a tripot type constant velocity universaljoint, and in particular to a tripot type constant velocity universaljoint of the type which uses cylindrical rollers and is suitable for usein an automotive vehicle.

2. Related Background Art

In the prior-art tripot type constant velocity universal joint, thetrack of one rotary member is a concave cylindrical surface and theperiphery of a roller loosely fitted onto the trunnion of the otherrotary member and engaged with said track, is a convex sphericalsurface. When the joint rotates under a torque with a joint anglepresent, an axial force is generated on the joint shaft three times perone full rotation of the joint. This axial force is increased ordecreased by the influences of the joint angle, the transmitted torque,etc. When the prior-art tripot type constant velocity universal joint isapplied to the axle of an automotive vehicle, particularly a vehiclewith high-output engine, the axial force becomes great. There has alsobeen a problem that when the cycle, of generation of such axial forcecoincides with the natural frequency of the vehicle body, the suspensionor the like and an axial force great enough to cause resonance of thevehicle body, is generated the vehicle seat occupant feels an unpleasantlateral vibration of the vehicle. This has in turn led to inconveniencein the design of a vehicle in that the joint angle must be limited to arelatively small angle.

In respect of this problem, U.S. Pat. No. 3,818,721 (Japanese PatentPublication No. 92448/1974) bears no description of the function and theeffect of positively decreasing the axial force, but discloses a tripottype constant velocity universal joint comprising track surfaces formedwith three pairs of parallel planar surfaces as a pair, and threedriving rollers each fixed for rotation and pivotal movement relative toa trunnion and having a cylindrical surface, and each maintained at apredetermined distance from the rotary shaft of the trunnions. Thisjoint has an advantage is that the contact between the rollers and thetrack surfaces takes place on the generating lines of the outerperipheries of the rollers and no axial force is generated on the axesof the rollers themselves.

However, in such cylindrical type construction according to the priorart, when the joint rotates with a certain angle, each roller rocks andturns on said driving surface and at this time, the roller is freelypivoted relative to the trunnion. Thus the direction of rolling movementof the roller relative to said driving surface is not perpendicular tothe axis of the trunnion, but is arbitrary. In such case, not only asliding resistance is produced between the rollers and the drivingsurface, but also a component of this sliding resistance force in theaxial direction of the trunnion acts on the rollers. Consequently, africtional resistance force produced in the portion which supports thiscomponent of force hampers smooth rotation of the rollers. These slidingresistance and frictional resistance forces lead to the generation ofthe axial force

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the problem of theprior art whereby an axial force is generated by resistance producedbetween the rollers and the track surfaces, due to the fact that the;cylindrical rollers are freely pivoted relative to the trunnions and thedirections of rolling movement of the rollers relative to the tracksurfaces are not perpendicular to the respective axes of the trunnion,but is arbitrary The gist of the present invention resides in a tripottype constant velocity universal joint comprising a rotary memberprovided with three tracks each consisting of two parallel planarsurfaces, and three cylindrical roller assemblies engaged with saidtracks respectively, characterized by the provision of pivoting meanspermitting the outer race of each of said cylindrical roller assembliesto pivot around a point on the axis of the corresponding trunnion, andpivot controlling means for controlling said pivot of said cylindricalroller assemblies. The tripot type constant velocity universal joint ofthe present invention is particularly of a construction in which thedirection of rolling movement of the cylindrical roller assemblies ispositively controlled.

With the above-described construction, the contact between said tracksand said cylindrical roller assemblies takes place on the generatinglines of the outer races of said cylindrical roller assemblies, and thedirection of rolling movement of said outer races is controlled to adirection perpendicular to the axes of the trunnions Therefore, thetransmitted force produced in said contact portion which acts in thenormal direction of the contact line, acts in a plane containing theaxes of the cylindrical roller assemblies, i.e. acts in a planecontaining the axes of the three trunnions, and no axial force isgenerated on the joint shaft perpendicular to this plane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view perpendicular to the rotaryshaft showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a simplified perspective view of a spider used in the firstembodiment.

FIG. 4 is a perspective view of an inner race used in the firstembodiment.

FIG. 5 is a front view showing the course of assembly in which the twoplanar portions of a trunnion in the first embodiment are adjusted inphase with the oval-shaped cut-aways of the inner race.

FIG. 6 is a front view of the inner race of FIG. 5 as it is rotatedcircumferentially by 90° and to which two guide plates are assembled.

FIG. 7A is a front view of the guide plate, and FIG. 7B is a side viewthereof.

FIG. 8 is a fragmentary cross-sectional view showing a second embodimentof the present invention.

FIG. 9 is a cross-sectional view taken along line 9--9 of FIG. 8.

FIG. 10 is a side view of the FIG. 8 second embodiment.

FIG. 11 is a fragmentary cross-sectional view showing a third embodimentof the present invention.

FIG. 12 is a cross-sectional view taken along line 12--12 of FIG. 11.

FIG. 13 is a fragmentary cross-sectional view showing a fourthembodiment of the present invention.

FIG. 14 is a cross-sectional view taken along line 14--14 of FIG. 13.

FIG. 15 is a fragmentary cross-sectional view showing a fifth embodimentof the present invention.

FIG. 16 is a cross-sectional view taken along line 16--16 of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of the present invention will hereinafter be describedwith reference to the drawings.

EMBODIMENT 1

A first embodiment shown in FIGS. 1 to 7 will hereinafter be describedin detail.

Referring to FIGS. 1 and 2, a housing 1, which is a first rotary member,is provided with three circumferentially equally spaced tracks 2 whichare constituted by two planar surfaces parallel to the axis of thehousing and facing parallel to each other. The housing 1 is connected toa transmission (not shown), etc. - for example, through a differentialgear or the like (not shown). A; spider 3, which is a second rotarymember and connected to wheels, for example, through another constantvelocity universal joint, is projectedly provided with three trunnionshafts 4 branching off from the boss portion 24 of the spider 3 andcircumferentially equally spaced apart. A cylindrical roller assembly 5engaging with each track 2 is loosely fitted on each trunnion shaft 4.The cylindrical roller assembly is comprised of a cylindrical outer race6 rolling on the track 2, an inner race 7 loosely fitted to the trunnionshaft 4, and needle rollers 8 constituting a plurality of rollingmembers interposed between the outer race 6 and the inner race 7. Theouter race 6 of the cylindrical roller assembly 5, with the needlerollers 8, has its axial movement limited by a snap ring 9 and a ring 10fitted on the outer diameter of the inner race 7. On the other hand,smooth rotation is ensured by the rolling movement of the needle rollers8. Further, as shown in FIG. 3, the outer diameter surface 11 of thetrunnion shaft 4 is of a convex spherical shape and a part thereofprovides two planar surfaces 12 formed parallel to a plane containingthe axes of the three trunnion shafts 4. The inner diameter surface 13of the inner race 7 is of a concave spherical shape which is inspherical surface contact with the outer diameter surface 11 of thetrunnion shaft 4, and an oval-shaped cut-away 14, shown in FIG. 4,extends through a portion of the inner diameter of the inner race 7axially of the inner race. Guide plates 15 are fitted to the oppositeends of the cut-away 14 and check the two planar surfaces 12 of thetrunnion shaft 4. The guide plates 15 are axially retained by a C-shapedsnap ring 16 fitted to an end of the trunnion shaft 4. By theabove-described construction, the outer race 6 of the cylindrical rollerassembly 5 is pivoted around a point on the axis of the trunnion shaft4, but controlled is such movement to a plane parallel to the planecontaining the axes of the three trunnion shafts 4 Therefore, thedirection of rolling movement of the outer race 6 relative to theaforementioned track is controlled to a direction perpendicular to theaxes of the trunnion shafts 4, whereby the generation of an axial forceis prevented, and the inclination of the trunnion shafts 4 by theeccentric movement of the center of the spider 3 in the plane containingthe axes of the three trunnion shafts 4 (which is peculiar to a tripottype constant velocity universal joint), is completely absorbed.

A method of assembling the present embodiment is shown in FIGS. 5 to 7.The inner race 7 is inserted onto the trunnion shaft 4 with the phasesof the two planar surface portions 12 of the trunnion shaft 4 and thesides of the cut-away 14 of the inner race 7 being adjusted to eachother. Then the inner race 7 is circumferentially rotated by 90° whenthe centers of the inner and outer spherical surfaces coincide with eachother, whereby the spherical surface portions fit to each other. Theaforementioned guide plates 15 are inserted into crescent spaces 17defined by the two planar surface portions 12 of the trunnion shaft 4and the cut-away 14 in the inner diameter of the inner race, and theC-shaped snap ring 16 is fitted thereto, whereupon the cylindricalroller assembly 5 is positioned axially to the trunnion shaft 4 andassembled.

The guide plates 15 fitted to the inner race 7 are pivoted with theinner race 7 relative to the trunnion shaft 4 only in a plane parallelto the two planar surfaces 12 of the trunnion shaft 4. For this reason,convex portions 19 are provided in the central portions of the oppositesides of the plate width so that the guide plates do not interfere withthe end portions 18 of said two planar surfaces at the root of thetrunnion shaft 4 and with the C-shaped snap ring 16 fitted to the end ofthe trunnion shaft 4.

EMBODIMENT 2

A second embodiment shown in FIGS. 8 to 10 will now be described indetail. In the first embodiment, the outer diameter of the trunnionshafts 4 is spherical, whereas in the present embodiment, the outerdiameter of trunnion shafts 20 is cylindrical and the trunnion comprisestrunnion shafts 20 and spherical bushings 22 fitted to the trunnionshafts 20 and fixed axially to the trunnion shafts 20 by snap rings 21,the outer diameter of the spherical bushings 22 being of a convexspherical shape. The inner diameter surface of an inner race 23 is of aconcave shape which is in spherical surface contact with the outerdiameter surface of the spherical bushings 22. The combination of thespherical surfaces can be accomplished by inserting the sphericalbushing 22 into a cut-away 50 in the inner race 23 and rotating thespherical bushing 22 by 90° when the centers of the inner and outerspherical surfaces coincide with each other. The pivot controlling meansin the present embodiment is of such a construction that a boss portion24 on which the trunnion shafts 20 are projectedly provided, hasprojections 25 that are arranged symmetrically with respect to the axesof the trunnion shafts 20, on a line perpendicular to a plane containingthe axes of the three trunnion shafts 20 and passing through the axes ofthe trunnion shafts 20. The projections 25 bear against the end surfaceof the inner race 23 to control the pivot, and the outer race 6 of acylindrical roller assembly 26 similar in construction to Embodiment 1pivots around a point on the axis of the trunnion shaft 20, but iscontrolled in such movement to a plane parallel to the plane containingthe axes of the three trunnion shafts 20. Therefore, the direction ofrolling movement of the outer race 6 is controlled to a directionperpendicular to the axis of the trunnion shaft 20 and the generation ofan axial force is prevented.

EMBODIMENT 3

A third embodiment shown in FIGS. 11 and 12 will now be described indetail. This embodiment is the same as the second embodiment except forthe pivot controlling means, and members similar to those in the secondembodiment are given similar reference numerals and the description ofthese members is omitted. The pivot controlling means in the presentembodiment is of a construction in which a bore 28 perpendicular to aplane containing the axes of three trunnion shafts 27 and passingthrough the axes of the trunnion shafts 27 is formed in the centralportion of each trunnion shaft 27 and a spherical bushing 30. A pin 29is resiliently mounted in the bore 28 by means of a spring 31 so thatthe tip end thereof protrudes from the outer diameter surface of aspherical bushing 30 and said tip end bears against a groove 33 formedin the inner diameter of an inner race 32 The outer race 6 of acylindrical roller assembly 34 pivots only in a direction around theaxis of the pin 29 and therefore, the direction of rolling movement ofthe outer race 6 is controlled to a direction perpendicular to the axesof the trunnion shaft 27, whereby the generation of an axial force isprevented.

In order to facilitate the assembly, the spherical bushing 30 may bedivided into two parts.

EMBODIMENT 4

A fourth embodiment shown in FIGS. 13 and 14 will now be described indetail The cylindrical roller assembly 43 of the present embodiment iscomprised of a cylindrical outer race 35 whose inner diameter surface isof a concave spherical shape, an inner race 36 whose outer diametersurface is of a convex spherical shape and which is fitted to and inspherical surface contact with the outer race 35 and is pivoted therein.A plurality of needle rollers 38 is interposed between the inner race 36and trunnion shafts 37, and a ring 39 and a snap ring 40 are fitted tothe end of each trunnion shaft 37 to limit the axial movement of theneedle rollers 38 and inner race 36 relative to the trunnion shaft 37.The pivot controlling means is of a construction in which a boss portion41 on which the trunnion shafts 37 are projectedly provided hasprojections 42 that are arranged symmetrically with respect to the axesof the trunnion shafts 37, on a line perpendicular to a plane containingthe axes of the three trunnion shafts 37 and passing through the axes ofthe trunnion shafts 37. The projections 42 bear against the end surfaceof the outer race 35 to control pivot. The outer race 35 of thecylindrical roller assembly 43 pivots around a point on the axis of thetrunnion shaft 37, but is controlled is such movement to a planeparallel to the plane containing the axes of the three trunnion shafts37. Therefore, the direction of rolling movement of the outer race iscontrolled to a direction perpendicular to the axes of the trunnions,whereby the generation of an axial force is prevented.

EMBODIMENT 5

A fifth embodiment shown in FIGS. 15 and 16 will now be described indetail This embodiment is the same as the fourth embodiment except forthe pivot controlling means, and members similar to those in the fourthembodiment are given similar reference numerals and the description ofthese members is omitted. The pivot controlling means in the presentembodiment is of a construction in which the end portion of eachtrunnion shaft 44 is provided with a pin bore 45 on a line perpendicularto a plane containing the axes of three trunnion shafts 44 and passingthrough the axis of the corresponding trunnion shafts 44. A pin 46 isinserted in the pin bore 45, and the opposite ends of the pin 46 bearagainst the end surface of an outer race 47 to control pivot. The outerrace 47 of a cylindrical roller assembly 48 pivots around a point on theaxis of the trunnion shaft 44, but is controlled in such movement to aplane parallel to the plane containing the axes of the three trunnionshafts 44. Therefore, the direction of rolling movement of the outerrace is controlled to a direction perpendicular to the axes of thetrunnion shafts 44, whereby the generation of an axial force isprevented.

As described above, the outer race of the cylindrical roller assemblysmoothly rolls on the track of the first rotary member while beingcontrolled its rolling movement to a direction perpendicular to the axisof the trunnion. Consequently, the sliding resistance and frictionresistance forces caused by the conventional cylindrical roller, whichpivots freely in all directions relative to the trunnion and rollsrelative to the track surface in other directions than a directionperpendicular to the axis of the trunnion, can be eliminated. Thusbecomes possible to prevent the generation of the axial force threetimes per one full rotation of the joint, and the use of such assembly,for example, in the joint portion of the axle of an automotive vehiclecan greatly reduce the unpleasant reaction of a the vehicle seatoccupant caused by the lateral vibration of the vehicle body.

It should be understood that the present invention is not restricted tothe embodiments illustrated herein, but various modifications andchanges can be made therein without departing from the scope of theinvention as defined in the appended claims.

I claim:
 1. A tripot type constant velocity universal joint,comprising:a first rotary member provided with three pairs of parallelplanar track surface pairs, a second rotary member having threetrunnions corresponding to said track surface pairs, a respectivecylindrical roller assembly loosely fitted to each trunnion and engagedwith the corresponding track surface pair, said roller assemblycomprising a cylindrical outer race rolling on the corresponding tracksurface pair, an inner race loosely fitted to said outer race, and aplurality of rolling members interposed between said inner race and saidtrunnion, said inner race being axially constrained on said trunnion andhaving outer peripheral surface portions of convex spherical shape, andsaid outer race having inner peripheral surface portions of concavespherical shape in spherical surface contact with said outer peripheralsurface portions of said inner race such that said outer race ispivotably movable about a point on an axis of said trunnion, and pivotcontrolling means for restricting the pivotal movement of said outerrace to planes parallel to a plane perpendicular to a rotary axis ofsaid second rotary member, such that the direction of rolling movementof said outer race relative to the corresponding track surface pair isperpendicular to the axis of said trunnion.
 2. A tripot type constantvelocity universal joint according to claim 1, wherein said secondrotary member comprises a spider having a boss portion with saidtrunnions branching therefrom in three equally spaced part directions,and said pivot controlling means comprises at least one projectionarranged on said boss portion on a line which is perpendicular to aplane containing the axes of said three trunnions and which intersectsthe axis of said trunnion, each said projection bearing against an endsurface portion of said outer race to thereby control the pivotalmovement of said outer race.
 3. A tripot type constant velocityuniversal joint according to claim 1, wherein said pivot controllingmeans comprises a bore extending through an outer end portion of saidtrunnion in a direction perpendicular to a plane containing the axes ofsaid three trunnions, and a pin received in said bore and havingopposite ends bearing against end surface portions of said outer race tothereby control the pivotal movement of said outer race.